JP6287099B2 - Reflective mask blank for EUV lithography - Google Patents

Description

  The present invention relates to a reflective mask blank (hereinafter referred to as “EUV mask blank”) for EUV (Extreme Ultra Violet) lithography used in semiconductor manufacturing and the like, and the EUV mask blank. The present invention relates to a reflective mask for EUV lithography (hereinafter referred to as “EUV mask” in the present specification) formed on an absorption layer.

  2. Description of the Related Art Conventionally, in the semiconductor industry, a photolithography method using visible light or ultraviolet light has been used as a technique for transferring a fine pattern necessary for forming an integrated circuit having a fine pattern on a Si substrate or the like. However, while miniaturization of semiconductor devices is accelerating, the limits of conventional photolithography methods have been approached. In the case of the photolithography method, the resolution limit of the pattern is about ½ of the exposure wavelength, and it is said that the immersion wavelength is about ¼ of the exposure wavelength, and the immersion of ArF laser (193 nm) is used. Even if the method is used, the limit of about 45 nm is expected. Therefore, EUV lithography, which is an exposure technique using light in the EUV wavelength region shorter than the ArF laser (hereinafter referred to as “EUV light”), is promising as an exposure technique for 45 nm and beyond. In this specification, EUV light refers to light having a wavelength in the soft X-ray region or vacuum ultraviolet region, and specifically refers to light having a wavelength of about 10 to 20 nm, particularly about 13.5 nm ± 0.3 nm.

  Since EUV light is easily absorbed by any material and the refractive index of the material is close to 1 at this wavelength, a conventional refractive optical system such as photolithography using visible light or ultraviolet light cannot be used. For this reason, in the EUV light lithography, a reflective optical system, that is, an EUV mask and a mirror are used.

  The mask blank is a stacked body before a mask pattern is formed on the photomask. The EUV mask blank has a structure in which a reflective layer that reflects EUV light and an absorption layer that absorbs EUV light are formed in this order on a substrate such as glass (see Patent Document 1). For the absorption layer, a material having a high absorption coefficient for EUV light, specifically, a material mainly composed of Ta, for example, is used.

  Patent Document 1 discloses that a tantalum boron alloy nitride (TaBN), a tantalum boron alloy oxide (TaBO), and a tantalum boron alloy oxynitride (TaBNO) have a high absorption coefficient for EUV light. Since the reflectivity of deep ultraviolet light in the wavelength region of pattern inspection light (about 190 nm to 260 nm) is low, it is considered preferable as a material for the absorption layer.

  In recent years, in EUV mask blanks, it has been desired to reduce the thickness of the absorption layer. In EUV lithography, exposure light is not irradiated from the vertical direction with respect to the EUV mask, but is irradiated from a direction inclined several degrees, usually 6 degrees from the vertical direction. At this time, if the absorption layer is thick, a shadow caused by exposure light is generated in the mask pattern formed by removing a part of the absorption layer by etching during EUV lithography, and an Si wafer is formed using the EUV mask. The shape accuracy and dimensional accuracy of a mask pattern (hereinafter referred to as “transfer pattern”) transferred to a resist on a substrate such as the above are likely to deteriorate. This problem becomes more prominent as the line width of the mask pattern formed on the EUV mask becomes smaller. Therefore, it is required to make the absorption layer of the EUV mask blank thinner.

As described above, a material having a high absorption coefficient for EUV light is used for the absorption layer of the EUV mask blank. When the EUV light is irradiated on the surface of the absorption layer, the irradiated EUV light is absorbed by the absorption layer. The film thickness that is completely absorbed is ideal. However, as described above, since it is required to reduce the thickness of the absorption layer, the irradiated EUV light cannot be completely absorbed by the absorption layer, and part of it becomes reflected light.
What is required when forming a transfer pattern on a resist on a substrate by EUV lithography using an EUV mask is the contrast of reflected light in the EUV wavelength region (hereinafter referred to as “EUV reflected light”), that is, a mask pattern. This is a contrast between EUV reflected light from a portion where the absorbing layer is removed during formation and the reflective layer is exposed, and EUV reflected light from a portion where the absorbing layer is not removed during mask pattern formation. Therefore, as long as the contrast of the EUV reflected light can be sufficiently secured, it has been considered that there is no problem even if the irradiated EUV light is not completely absorbed by the absorption layer.

  Based on the above idea, an EUV mask using the principle of phase shift has been proposed in order to reduce the thickness of the absorption layer (Patent Document 2). This is because the EUV reflected light from the part where the absorption layer was not removed at the time of mask pattern formation has a reflectance of 3 to 15%, and the part where the absorption layer was removed and the reflection layer was exposed at the time of mask pattern formation It has a phase difference of 175 to 185 degrees with respect to the EUV reflected light from. Since this EUV mask can sufficiently maintain the contrast with the reflective layer using the principle of phase shift with respect to the EUV reflected light from the absorbing layer, the thickness of the absorbing layer can be reduced. It is described.

Japanese Patent Laid-Open No. 2004-6798 JP 2006-228766 A

  However, in the case of an absorption layer mainly composed of Ta as described in Patent Document 1, the minimum thickness of the absorption layer is limited to 50 to 60 nm. The film thickness that becomes the limit when the absorption layer is made thin depends greatly on the refractive index n and extinction coefficient k of the metal as the main component.

In general, the phase difference between the reflective layer and the absorbing layer is represented by the following equation.
φ = 4π (1-n) × d × cos θ / λ
Here, φ: retardation, n: refractive index of absorbing layer, d: film thickness of absorbing layer, θ: incident angle of EUV light, λ: wavelength of EUV light.
When the phase difference φ is 180 ° (= π), the reflection contrast is maximized. The film thickness at that time is represented by the following formula.
d = λ / {4 (1-n) × cos θ}
That is, the smaller the refractive index n of the absorbing layer, the more advantageous the thinning of the absorbing layer. For example, in the case of an absorption layer mainly composed of Ta, the refractive index is n≈0.945. Therefore, if the refractive index of the absorption layer is less than 0.945, the film can be further thinned. The extinction coefficient k is preferably k = 0.020 to 0.080 in order to obtain a reflectance of 2 to 30%.
Therefore, the absorption layer preferably has a refractive index of less than 0.945 and an extinction coefficient k of 0.020 to 0.080 for thinning.

  Patent Document 2 describes a range of optical constants that are optimum for a halftone film (corresponding to an absorption layer). As an example, optical characteristics for a single layer structure of titanium (Ti) or tungsten (W) are described. It is described. However, in the case of the halftone film in Patent Document 2, the optimum film thickness at which the phase difference between the reflective layer and the halftone film is 175 to 185 degrees inevitably depends on the optical constant for the EUV wavelength of the halftone film. It will be decided to a specific film thickness. Therefore, as shown in FIG. 3, when the optimum film thickness of the halftone film is in the vicinity where the phase difference change with respect to the film thickness change becomes large, strict film thickness control of the halftone film is required, which is not preferable in production. .

  In order to solve the above-described problems of the prior art, the present invention sets the phase difference between the reflective layer and the absorbing layer in a range near 180 °, and reflects the reflective layer and the absorbing layer with respect to the change in the thickness of the absorbing layer. The object of the present invention is to provide an EUV mask blank that has a structure of an absorption layer that is controlled so that a change in phase difference between the first and second phase differences is small, and that can be expected to be thinner than a conventional absorption layer.

  As a result of intensive studies to solve the above-mentioned problems, the inventors of the present invention have an absorption layer composed of a surface-side layer (upper layer) and a substrate-side layer (lower layer), and one of the upper layer and the lower layer is formed. A chromium-based film containing chromium (Cr) as a main component and at least one of oxygen (O) and nitrogen (N), and the other as a main component containing tantalum (Ta) and palladium (Pd), and O and By making a TaPd-based film containing at least one of N, the phase difference between the reflective layer and the absorption layer is in the range of about 180 °, and the reflection layer and the absorption layer with respect to the change in film thickness of the absorption layer It has been found that the change in phase difference between the first absorption layer and the second absorption layer can be controlled to be small, and the film can be made thinner than the conventional absorption layer.

The present invention has been made on the basis of the above findings, and a reflective mask for EUV lithography in which a reflective layer that reflects EUV light and an absorbing layer that absorbs EUV light are formed in this order on a substrate. Blank,
The absorption layer is composed of a surface side layer (upper layer) and a substrate side layer (lower layer),
One of the upper layer and the lower layer of the absorption layer is a Cr-based film containing chromium (Cr) as a main component and containing at least one of oxygen (O) and nitrogen (N).
The other is a TaPd-based film containing tantalum (Ta) and palladium (Pd) as main components and containing at least one of oxygen (O) and nitrogen (N).
The absorption layer provides a reflective mask blank for EUV lithography that satisfies the following (1) to (5) (hereinafter referred to as “EUV mask blank of the present invention”).
(1) The total film thickness (L) of the absorption layer is not less than 30 nm and not more than 45 nm.
(2) The film thickness of the TaPd-based film is 8 nm or more and 36 nm or less.
(3) The peak reflectance of EUV light on the surface of the absorption layer is 5% or more and 12% or less.
(4) The phase difference (φ) between the EUV reflected light on the surface of the reflective layer and the EUV reflected light on the surface of the absorbing layer is in the range of 180 ° ± 10 °.
(5) The gradient (Δφ / ΔL) of the change (Δφ) in the phase difference (φ) with respect to the change (ΔL) in the total film thickness (L) of the absorption layer is 15 deg / nm or less.

  In the EUV mask blank of the present invention, the Cr-based film is a CrN film containing Cr and N, the Cr content is 40 to 97 at%, the N content is 3 to 60 at%, The total content of Cr and N is preferably 95 to 100 at%.

  In the EUV mask blank of the present invention, the TaPd-based film is a TaPdN film containing Ta, Pd and N, the Ta content is 10 to 60 at%, and the Pd content is 20 to 70 at% , N is preferably 10 to 70 at%, and the total content of Ta, Pd, and N is preferably 95 to 100 at%.

  In the EUV mask blank of the present invention, at least one of the Cr-based film and the TaPd-based film further contains hydrogen (H), silicon (Si), and boron (B) in an amount of 0.1 to 10 at%. You may contain by a total content rate.

  In the EUV mask blank of the present invention, the upper layer has a two-layer structure of the CrN film and a surface protective layer formed on the CrN film, the surface protective layer contains Cr and O, Cr A CrO film having a content of 15 to 70 at% and an O content of 30 to 85 at%, or containing Cr, O and N, a Cr content of 10 to 60 at%, and a total of O and N The CrON film | membrane whose content rate is 40-90 at% and whose composition ratio of O and N is O: N = 9: 1-6: 4 may be sufficient.

In the EUV mask blank of the present invention, the upper layer has a two-layer structure of the TaPdN film and a surface protective layer formed on the TaPdN film, and the surface protective layer contains Ta, Pd and O. A TaPdO film having an O content of 30 to 85 at%, or containing Ta, Pd, O, and N, a total content of O and N being 40 to 90 at%, and a composition ratio of O and N is O: A TaPdON film in which N = 9: 1 to 6: 4 may be used.
The TaPdO film preferably has a Ta content of 7 to 32 at%, a Pd content of 8 to 38 at%, and an O content of 30 to 85 at%.
The TaPdON film has a Ta content of 5 to 27 at%, a Pd content of 5 to 33 at%, a total content of O and N of 40 to 90 at%, and a composition of O and N The ratio is preferably O: N = 9: 1 to 6: 4.

  In the EUV mask blank of the present invention, it is preferable that the film thickness of the surface protective layer is 0.5 nm or more and 5 nm or less.

  In the EUV mask blank of the present invention, the surface protective layer may further contain hydrogen (H), silicon (Si), and boron (B) at a total content of 0.1 to 10 at%.

  In the EUV mask blank of the present invention, the absorption layer preferably has an amorphous crystal state.

  In the EUV mask blank of the present invention, the surface roughness (rms) of the absorption layer surface is preferably 0.5 nm or less.

  In the EUV mask blank of the present invention, a protective layer is formed between the reflective layer and the absorbing layer to protect the reflective layer when forming a pattern on the absorbing layer. It is preferable to use a Ru compound as a constituent material.

  In the EUV mask blank of the present invention, when a protective layer made of Ru or Ru compound is formed, it is preferable that the upper layer is the TaPd-based film and the lower layer is the Cr-based film.

In the EUV mask blank of the present invention, the Cr-based film is a CrN film, and the CrN film is at least one of helium (He), argon (Ar), neon (Ne), krypton (Kr), and xenon (Xe). It is preferably formed by performing a sputtering method using a target containing chromium (Cr) in an inert gas atmosphere containing one and nitrogen (N ₂ ).

In the EUV mask blank of the present invention, the TaPd-based film is a TaPdN film, and the TaPdN film is helium (He), argon (Ar), neon (Ne), krypton (Kr), or xenon (Xe). It can be formed by performing a sputtering method using a target containing tantalum (Ta) and palladium (Pd) in an inert gas atmosphere containing at least one and nitrogen (N ₂ ). preferable.

In the EUV mask blank of the present invention, the surface protective layer is a TaPdO film, and the TaPdO film is at least one of helium (He), argon (Ar), neon (Ne), krypton (Kr), and xenon (Xe). Preferably, it is formed by performing a sputtering method using a target containing tantalum (Ta) and palladium (Pd) in an inert gas atmosphere containing oxygen and oxygen (O ₂ ). .

In the EUV mask blank of the present invention, the surface protective layer is a TaPdON film, and the TaPdON film is at least one of helium (He), argon (Ar), neon (Ne), krypton (Kr), and xenon (Xe). By performing sputtering using a target containing tantalum (Ta) and palladium (Pd) in an inert gas atmosphere containing oxygen and oxygen (O ₂ ) and nitrogen (N ₂ ) Preferably it is formed.

In the EUV mask blank of the present invention, the surface protective layer is a CrO film, and the CrO film is at least one of helium (He), argon (Ar), neon (Ne), krypton (Kr), and xenon (Xe). It is preferably formed by performing a sputtering method using a target containing chromium (Cr) in an inert gas atmosphere containing one and oxygen (O ₂ ).

In the EUV mask blank of the present invention, the surface protective layer is a CrON film, and the CrON film is at least one of helium (He), argon (Ar), neon (Ne), krypton (Kr), and xenon (Xe). One is preferably formed by performing a sputtering method using a target containing chromium (Cr) in an inert gas atmosphere containing oxygen (O ₂ ) and nitrogen (N ₂ ).

  The present invention also provides a reflective mask for EUV lithography in which the absorption layer of the EUV mask blank of the present invention is patterned.

  The EUV mask blank of the present invention is thinner than the conventional absorption layer by making the refractive index value for EUV light smaller than the conventional absorption layer mainly composed of Ta and further having a desired extinction coefficient. It is possible. Therefore, it is expected to improve the shape accuracy and dimensional accuracy of a transfer pattern transferred to a resist on a substrate such as a Si wafer.

  In addition, since the change of the phase difference with respect to the change in film thickness is small in the vicinity of the film thickness where the phase difference φ between the reflective layer and the absorption layer is 180 ° ± 10 °, an acceptable film in the film formation process of the absorption layer The range of thickness can be widened.

FIG. 1 is a schematic cross-sectional view showing an embodiment of the EUV mask blank of the present invention. FIG. 2 is a schematic cross-sectional view showing another embodiment of the EUV mask blank of the present invention. FIG. 3 is a graph plotting the relationship between the thickness (L) of the absorption layer and the phase difference (φ) with respect to EUV light. FIG. 4 is a schematic sectional view showing still another embodiment of the EUV mask blank of the present invention. FIG. 5 is a schematic sectional view showing still another embodiment of the EUV mask blank of the present invention.

Hereinafter, the EUV mask blank of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic cross-sectional view showing an embodiment of the EUV mask blank of the present invention. In the mask blank 1 shown in FIG. 1, a reflective layer 12 that reflects EUV light and an absorption layer 14 that absorbs EUV light are formed on a substrate 11 in this order. A protective layer 13 for protecting the reflective layer 12 is formed between the reflective layer 12 and the absorbent layer 14 when a pattern is formed on the absorbent layer 14. The EUV mask blank 1 of the present invention, the absorption layer 14 is composed of a upper layer 14a and lower layer 14b. However, in the EUV mask blank 1 of the present invention, only the substrate 11, the reflective layer 12 and the absorption layer 14 (upper layer 14a and lower layer 14b) are essential in the configuration shown in FIG. 1, and the protective layer 13 is an optional component. is there.
Hereinafter, individual components of the mask blank 1 will be described.

The substrate 11 is required to satisfy the characteristics as a substrate for an EUV mask blank. Therefore, the substrate 11 has a low thermal expansion coefficient (specifically, the thermal expansion coefficient at 20 ° C. is preferably 0 ± 1.0 × 10 ⁻⁷ / ° C., more preferably 0 ± 0.3 × 10 ⁻⁷ / ° C. More preferably 0 ± 0.2 × 10 ⁻⁷ / ° C., further preferably 0 ± 0.1 × 10 ⁻⁷ / ° C., particularly preferably 0 ± 0.05 × 10 ⁻⁷ / ° C.) Those having excellent smoothness, flatness, and resistance to a cleaning liquid used for cleaning a mask blank or a photomask after pattern formation are preferred. Specifically, the substrate 11 is made of glass having a low thermal expansion coefficient, such as SiO ₂ —TiO ₂ glass, but is not limited thereto, and is not limited to crystallized glass, quartz glass, silicon, A substrate such as metal can also be used. A film such as a stress correction film may be formed on the substrate 11.

Since the substrate 11 has a smooth surface with a surface roughness (rms) of 0.15 nm or less and a flatness of 100 nm or less, a high EUV light reflectance and transfer accuracy can be obtained in a photomask after pattern formation. Therefore, it is preferable. In addition, in this specification, surface roughness is demonstrated as the root mean square roughness Rq (old RMS) based on JIS-B0601.
The size, thickness, etc. of the substrate 11 are appropriately determined according to the design value of the mask. In the examples described later, SiO ₂ —TiO ₂ glass having an outer shape of 6 inches (152 mm) square and a thickness of 0.25 inches (6.3 mm) was used.
It is preferable that the surface of the substrate 11 on the side where the reflective layer 12 is formed has no defects. However, even if it exists, the depth of the concave defect and the height of the convex defect are not more than 2 nm so that the phase defect does not occur due to the concave defect and / or the convex defect. It is preferable that the half width of the defect and the convex defect is 60 nm or less.

  The reflective layer 12 is required to have a high EUV light reflectivity as a reflective layer of an EUV mask blank. Specifically, when the surface of the reflective layer 12 is irradiated with EUV light at an incident angle of 6 degrees, the maximum value of the light reflectance near the wavelength of 13.5 nm is preferably 60% or more, more preferably 63% or more, 65% or more is more preferable. Even when the protective layer 13 is provided on the reflective layer 12, the maximum value of the light reflectance near the wavelength of 13.5 nm is preferably 60% or more, more preferably 63% or more, and 65% or more. Is more preferable.

  Since the reflective layer 12 can achieve a high reflectance of EUV light, normally, a high refractive layer showing a high refractive index for EUV light and a low refractive index layer showing a low refractive index for EUV light are alternately arranged. A multilayer reflective film laminated a plurality of times is used as the reflective layer 12. In the multilayer reflective film forming the reflective layer 12, Si is widely used for the high refractive index layer, and Mo is widely used for the low refractive index layer. That is, the Mo / Si multilayer reflective film is the most common. However, the multilayer reflective film is not limited to this, and Ru / Si multilayer reflective film, Mo / Be multilayer reflective film, Mo compound / Si compound multilayer reflective film, Si / Mo / Ru multilayer reflective film, Si / Mo / Ru / Mo multilayer reflective films and Si / Ru / Mo / Ru multilayer reflective films can also be used.

  The thickness of each layer constituting the multilayer reflective film constituting the reflective layer 12 and the number of repeating units of the layers can be appropriately selected according to the film material used and the reflectance of EUV light required for the reflective layer. Taking the Mo / Si reflective film as an example, in order to make the reflective layer 12 having a maximum reflectance of EUV light of 60% or more, the multilayer reflective film has a film thickness of 2.3 ± 0.1 nm, A Si film having a thickness of 4.5 ± 0.1 nm may be laminated so that the number of repeating units is 30 to 60.

In addition, what is necessary is just to form each layer which comprises the multilayer reflective film which comprises the reflective layer 12 so that it may become desired thickness using well-known film-forming methods, such as a magnetron sputtering method and an ion beam sputtering method. For example, when forming a Mo / Si multilayer reflective film by using ion beam sputtering, an Si target is used as a target, and Ar gas (gas pressure 1.3 × 10 ⁻² Pa to 2.7 × 10 ⁻ is used as a sputtering gas. ² Pa), an Si film is formed to have a thickness of 4.5 nm at an ion acceleration voltage of 300 to 1500 V and a film formation rate of 0.03 to 0.30 nm / sec. using a target, using an Ar gas as a sputtering gas (gas pressure ^{1.3 × 10 -2 Pa~2.7 × 10 -2} Pa), an ion acceleration voltage 300 to 1,500 V, the deposition rate of 0.03 to 0 It is preferable to form the Mo film so that the thickness is 2.3 nm at 30 nm / sec. With this as one period, the Mo / Si multilayer reflective film is formed by laminating 30 to 60 periods of the Si film and the Mo film.

  In order to prevent the surface of the reflective layer 12 from being oxidized, the uppermost layer of the multilayer reflective film forming the reflective layer 12 is preferably a layer made of a material that is difficult to be oxidized. The layer of material that is not easily oxidized functions as a cap layer of the reflective layer 12. A Si layer can be exemplified as a specific example of the layer of a material that is hardly oxidized and functions as a cap layer. When the multilayer reflective film forming the reflective layer 12 is a Mo / Si multilayer reflective film, the uppermost layer can be made to function as a cap layer by making the uppermost layer an Si layer. In that case, the thickness of the cap layer is preferably 11 ± 2 nm.

The protective layer 13 is provided for the purpose of protecting the reflective layer 12 so that the reflective layer 12 is not damaged by the etching process when the absorption layer 14 is patterned by an etching process, usually a dry etching process. Therefore, as the material of the protective layer 13, a material that is not easily affected by the etching process of the absorption layer 14, that is, the etching rate is slower than that of the absorption layer 14 and is not easily damaged by the etching process is selected. The protective layer 13 of the present invention uses Ru or a Ru compound (RuB, RuSi, RuNb, etc.) as a constituent material.
Further, it is preferable that Ta and Cr are not included in the protective layer 13 for the purpose of preventing a decrease in the reflectance of EUV light from the surface of the protective layer 13. The content of Ta and Cr in the protective layer 13 is preferably 5 at% or less, particularly preferably 3 at% or less, and further preferably does not contain Ta and Cr.
The thickness of the protective layer 13 is preferably 1 to 60 nm, particularly preferably 1 to 10 nm.

The protective layer 13 is formed using a known film formation method such as magnetron sputtering or ion beam sputtering. When a Ru film is formed by magnetron sputtering, a Ru target is used as a target, Ar gas (gas pressure: 1.0 × 10 ⁻² Pa to 10 × 10 ⁻¹ Pa) is used as a sputtering gas, and an input voltage is 30 V. It is preferable to form a film so that the thickness is 2 to 5 nm at ˜1500 V and a film formation rate of 0.02 to 1.0 nm / sec.

The characteristic particularly required for the absorption layer 14 is that the contrast between the EUV light reflected by the reflection layer 12 and the EUV light reflected by the absorption layer 14 is high. In the case of an EUV mask that maintains the contrast with the reflective layer 12 by utilizing the principle of phase shift instead of absorbing the EUV light only with the absorbing layer 14, as described above, the refractive index n of the absorbing layer and The extinction coefficient k needs to be a desired value, and n is preferably less than 0.945, more preferably less than 0.930, and even more preferably less than 0.920. k is preferably 0.020 to 0.080, more preferably 0.025 to 0.078, and even more preferably 0.030 to 0.075.
In order to use the principle of phase shift, the peak reflectivity of EUV light on the surface of the absorption layer 14, specifically, when the EUV light is irradiated on the surface of the absorption layer 14 at an incident angle of 6 degrees, The maximum reflectance (peak reflectance) of light near 13.5 nm is preferably 5% or more and 12% or less.

The absorption layer 14 of the EUV mask blank 1 of the present invention is composed of a surface-side layer (upper layer 14a) and a substrate 11-side layer (lower layer 14b), and one of the upper layer 14a and the lower layer 14b is chromium (Cr). Is a Cr-based film containing at least one of oxygen (O) and nitrogen (N), the other is mainly composed of tantalum (Ta) and palladium (Pd), and at least one of O and N The above-mentioned characteristics are achieved by using a TaPd-based film containing and satisfying the following conditions (1) to (5).
(1) The total film thickness (L) of the absorption layer 14 is 30 nm or more and 45 nm or less.
(2) The thickness of the TaPd-based film is 8 nm or more and 36 nm or less.
(3) The peak reflectance of EUV light on the surface of the absorption layer 14 is 5% or more and 12% or less.
(4) The phase difference (φ) between the EUV reflected light on the surface of the reflective layer 12 and the EUV reflected light on the surface of the absorbing layer 14 is in the range of 180 ° ± 10 °.
(5) The gradient (Δφ / ΔL) of the change (Δφ) in the phase difference (φ) with respect to the change (ΔL) in the total film thickness (L) of the absorption layer 14 is 15 deg / nm or less.

  Examples of the Cr-based film include a CrO film containing Cr and O, a CrN film containing Cr and N, and a CrON film containing Cr, O and N. Among the Cr-based films exemplified above, the CrN film is preferable because it has a small refractive index with respect to EUV light and works advantageously for reducing the thickness of the absorption layer.

The Cr content in the CrN film is preferably 40 to 97 at%, because it has a low refractive index with respect to EUV light, which is advantageous for reducing the thickness of the absorption layer, and is more preferably 45 to 97 at%. Preferably, 45 to 95 at% is more preferable.
Further, the N content in the CrN film is preferably 3 to 60 at% for the reason that the film stress can be reduced, more preferably 3 to 55 at%, and further preferably 5 to 55 at%. When Cr is less than 40 at% (that is, N is more than 60 at%), desired optical characteristics cannot be obtained. Furthermore, when Cr is over 97 at% (that is, N is less than 3 at%), there is a problem that the film stress increases.
The total content of Cr and N in the CrN film is preferably 95 to 100 at%, more preferably 97 to 100 at%, and further preferably 99 to 100 at%.

  The Cr-based film in the present invention may further contain hydrogen (H), silicon (Si), and boron (B). When the Cr-based film contains H, Si, and B, the total content thereof is 0.1 to 10 at%, particularly 0.1 to 5 at%, and the film crystal structure can be made amorphous, and the absorption layer It is preferable because it contributes to smoothing the surface.

Examples of the TaPd-based film include a TaPdO film containing Ta, Pd and O, a TaPdN film containing Ta, Pd and N, and a TaPdON film containing Ta, Pd, O and N.
Among the TaPd-based films exemplified above, the TaPdN film is preferable because it has a low refractive index with respect to EUV light and thus works advantageously for reducing the thickness of the absorption layer.

A Ta content of 10 to 60 at% in the TaPdN film is preferable because it has a low refractive index with respect to EUV light, and is advantageous for reducing the thickness of the absorption layer, and more preferably 10 to 55 at%. 10 to 50 at% is more preferable.
Further, when the content of Pd in the TaPdN film is 20 to 70 at%, the refractive index is low with respect to EUV light. More preferred is 25 to 65 at%.
In addition, if the content of N in the TaPdN film is 10 to 70 at%, the refractive index is low with respect to EUV light, and therefore the film stress can be reduced and the film stress can be reduced. For reasons, it is preferably 10 to 60 at%, more preferably 10 to 50 at%. If the Ta content exceeds 60 at% or the Pd content is less than 20 at%, desired optical characteristics may not be obtained. Further, when the Ta content is less than 10 at% or the Pd content is more than 70 at%, there is a problem that the etching rate becomes slow. Furthermore, when the N content exceeds 70 at%, there is a possibility that desired optical characteristics may not be obtained. When the N content is less than 10 at%, there is a problem that the film stress increases.
The total content of Ta, Pd and N in the TaPdN film is preferably 95 to 100 at%, more preferably 97 to 100 at%, and further preferably 99 to 100 at%.

  The TaPd-based film in the present invention may further contain hydrogen (H), silicon (Si), and boron (B). When the TaPd-based film contains H, Si, and B, if the total content thereof is 0.1 to 10 at%, particularly 0.1 to 5 at%, the film crystal structure can be made amorphous, and the absorption layer surface It is preferable because it contributes to smoothing.

About the absorption layer 14, the reasoning of the said conditions (1)-(5) is shown below.
When the total film thickness (L ) of the absorbing layer 14 is less than 30 nm for the condition (1) , the phase difference (φ) between the EUV reflected light on the surface of the reflecting layer 12 and the EUV reflected light on the surface of the absorbing layer 14 is , Not within the range of 180 ° ± 10 °.
On the other hand, when the total film thickness (L) of the absorption layer 14 exceeds 45 nm, the peak reflectance of EUV light on the surface of the absorption layer 14 is less than 5%. Alternatively, the phase difference (φ) between the EUV reflected light on the surface of the reflective layer 12 and the EUV reflected light on the surface of the absorption layer 14 does not fall within the range of 180 ° ± 10 °.
30 nm or more and 43 nm or less are preferable, and, as for the total film thickness (L) of the absorption layer 14, 30 nm or more and 40 nm or less are more preferable.

Regarding condition (2), when the film thickness of the TaPd-based film is less than 8 nm, the peak reflectance of EUV light on the surface of the absorption layer 14 is less than 5%. Alternatively, the phase difference (φ) between the EUV reflected light on the surface of the reflective layer 12 and the EUV reflected light on the surface of the absorption layer 14 does not fall within the range of 180 ° ± 10 °.
On the other hand, when the film thickness of the TaPd-based film is more than 36 nm, the following points are problematic.
When forming a pattern on the absorption layer 14, a part of the absorption layer 14 is removed by a dry etching process. Since the absorption layer 14 of the present invention is composed of the upper layer 14a and the lower layer 14b having different constituent materials, the types of etching gases used in the dry etching process are different. In the case of a Cr-based film containing Cr as a main component, a chlorine-based gas (Cl ₂ , BCl ₃ ) is preferably used as an etching gas. On the other hand, a TaPd-based film containing Pd as a main component is preferably used as an etching gas using a fluorine-based gas (CF ₄ , CF ₃ H). However, in the case of a TaPd-based film, the etching rate when the dry etching process is performed is ½ that of a conventional Ta-based film (for example, TaN, TaNH, TaBN) that contains Ta as a main component and does not contain Pd. It is slow with about 1/6. For this reason, when the thickness of the TaPd-based film exceeds 36 nm, a slow etching rate becomes a problem when a dry etching process is performed for the purpose of forming a pattern on the absorption layer 14.
Further, the thickness of the TaPd-based film is preferably 8 nm or more and 34 nm or less, more preferably 8 nm or more and 32 nm or less, further preferably 8 nm or more and 30 nm or less, further preferably 8 nm or more and 25 nm or less, further preferably 8 nm or more and 23 nm or less, and more preferably 8 nm. More preferably, it is 20 nm or less.

The TaPd-based film may be either the upper layer 14a or the lower layer 14b constituting the absorption layer 14. When the upper layer 14a is a TaPd-based film, the Cr-based film becomes the lower layer 14b, and the lower layer 14b becomes the TaPd-based film. In this case, the Cr-based film becomes the upper layer 14a. When the upper layer 14a of the mask blank 1 shown in FIG. 1 is a TaPd-based film, the mask blank 1 shown in FIG.
However, when the mask blank 1 has the protective layer 13 made of Ru or Ru compound as a constituent material, a combination in which the upper layer 14a is a TaPd-based film and the lower layer 14b is a Cr-based film is preferable for the following reason. There is. As described above, a chlorine-based gas is used as an etching gas when the Cr-based film dry etching process is performed. The dry etching process using a chlorine-based gas causes little damage to the protective layer 13 made of Ru or Ru compound. Therefore, when the lower layer 14b is a Cr film, it is possible to reduce damage to the protective layer 13 made of Ru or Ru compound immediately below it as a constituent material.
On the other hand, in a combination configuration in which the upper layer 14a is a Cr-based film and the lower layer 14b is a TaPd-based film, it may be preferable for the following reasons. As described above, when performing the dry etching process of the TaPd-based film, a fluorine-based gas is used as an etching gas. Cr-based film of the upper layer 1 4a is highly resistant to dry etching process using a fluorine-based gas. Therefore, when the TaPd-based film of the lower layer 14b is dry-etched with a fluorine-based gas, the Cr-based film of the upper layer 14a acts as a hard mask, so that the resist applied for pattern formation can be thinned, and the pattern fine Works favorably.

Regarding the condition (3), the peak reflectivity of EUV light on the surface of the absorption layer 14 is 5% or more and 12% or less because, as described above, it is preferable to use the principle of phase shift.
The peak reflectance of EUV light on the surface of the absorption layer 14 is preferably 5% or more and 11% or less, and more preferably 5% or more and 10% or less.
In addition, when forming the low reflection layer mentioned later on the absorption layer 14, it is preferable that the peak reflectance of EUV light in the surface of a low reflection layer satisfy | fills said range.

Regarding the condition (4) , the phase shift (φ) between the EUV reflected light on the surface of the reflective layer 12 and the EUV reflected light on the surface of the absorbing layer 14 is within the range of 180 ° ± 10 °. This is because the principle of
When the protective layer 13 is formed on the reflective layer 12, the phase difference between the EUV reflected light on the surface of the protective layer 13 and the EUV reflected light on the surface of the absorption layer 14 is φ. In this respect, the condition (5) is the same.

As shown in FIG. 3 for the condition (5), when the relationship between the total film thickness (L) of the absorbing layer 14 and the phase difference (φ) is plotted, a sine curve is obtained while alternately taking a maximum value and a minimum value. Make a curved line.
The gradient (Δφ / ΔL) of the change (Δφ) in the phase difference (φ) with respect to the change (ΔL) in the total film thickness (L) of the absorption layer 14 is set to 15 deg / nm or less in the condition (4), that is, This is for reducing the change in phase difference with respect to the change in film thickness when the film thickness is in the range of 180 ° ± 10 °.
When the condition (5) is satisfied, the phase difference with respect to the change of the film thickness ± 0.7 nm is within a range of 180 ° ± 10 °, and the allowable film thickness range can be widened in the film formation process of the absorption layer 14. . That is, even if the thickness of the absorption layer varies to the extent possible in the film formation process, the variation in the optical characteristics of the EUV light in the surface of the EUV mask blank and the optical characteristics of the EUV light for each EUV mask blank Variation (individual difference) can be suppressed.

The Cr-based film and the TaPd-based film constituting the upper layer 14a and the lower layer 14b of the absorption layer 14 are preferably amorphous in the crystalline state due to the above configuration. In this specification, the phrase “crystalline state is amorphous” includes a microcrystalline structure other than an amorphous structure having no crystal structure.
If the crystal state of the Cr-based film and the TaPd-based film constituting the upper layer 14a and the lower layer 14b is amorphous, the surface of the absorption layer 14 is excellent in smoothness.
In the EUV mask blank 1 of the present invention, the surface roughness (rms) of the surface of the absorption layer 14 obtained by the amorphous structure of the Cr-based film and the TaPd-based film constituting the upper layer 14a and the lower layer 14b is 0. .5 nm or less is preferable. Here, the surface roughness of the surface of the absorption layer 14 can be measured by using an atomic force microscope (Atomic Force Microscope). If the surface roughness of the surface of the absorption layer 14 is large, the edge roughness of the pattern formed on the absorption layer 14 increases, and the dimensional accuracy of the pattern deteriorates. Since the influence of edge roughness becomes more prominent as the pattern becomes finer, the surface of the absorption layer 14 is required to be smooth.
If the surface roughness (rms) of the surface of the absorption layer 14 is 0.5 nm or less, the surface of the absorption layer 14 is sufficiently smooth, and there is no possibility that the dimensional accuracy of the pattern deteriorates due to the influence of edge roughness. The surface roughness (rms) of the surface of the absorption layer 14 is more preferably 0.4 nm or less, and further preferably 0.3 nm or less.

  In addition, it can be confirmed by the X-ray diffraction (XRD) method that the crystalline state of the Cr-based film and the TaPd-based film constituting the upper layer 14a and the lower layer 14b is amorphous, that is, an amorphous structure or a microcrystalline structure. . If the crystalline state of the Cr-based film and the TaPd-based film constituting the upper layer 14a and the lower layer 14b has an amorphous structure or a microcrystalline structure, a sharp peak is not observed in the diffraction peak obtained by XRD measurement.

  When the total film stress of the Cr-based film and the TaPd-based film constituting the upper layer 14a and the lower layer 14b is within ± 200 MPa, particularly within ± 180 MPa, the shape of the mask transfer pattern transferred to the resist on the substrate such as an Si wafer This is preferable because accuracy and dimensional accuracy do not deteriorate.

  The Cr-based film and the TaPd-based film constituting the upper layer 14a and the lower layer 14b can be formed by performing a known film forming method, for example, a sputtering method.

When the Cr-based film is a CrN film, using a Cr target, at least one of helium (He), argon (Ar), neon (Ne), krypton (Kr), and xenon (Xe) and nitrogen (N ₂ ) And a sputtering method such as a magnetron sputtering method or an ion beam sputtering method may be performed in an inert gas atmosphere. The conditions for forming the CrN film will be described below, taking as an example the case where the inert gas atmosphere is an atmosphere containing Ar and N ₂ .
Forming conditions <br/> sputtering gas CrN film: mixed gas of Ar and N ₂ (Ar gas concentration 30~70vol%, N ₂ gas concentration 30~70vol%, gas pressure 0.5 × 10 ^-1 Pa~1. 0 Pa)
Input power: 300-2000W
Deposition rate: 0.0083 to 1 nm / sec
In the above description, the sputtering gas is a mixed gas of Ar and N _2. However, as the sputtering gas, a mixed gas of an inert gas other than Ar and N ₂ or a mixed gas of a plurality of inert gases N ₂ is used. When used, the total concentration of the inert gas is set to the same concentration range as the Ar gas concentration described above.

When the TaPd-based film is a TaPdN film, using a target containing Ta and Pd, at least one of helium (He), argon (Ar), neon (Ne), krypton (Kr), and xenon (Xe) , A sputtering method such as a magnetron sputtering method or an ion beam sputtering method is performed in an inert gas atmosphere containing nitrogen (N ₂ ).
Here, in the case of using a target containing Ta and Pd, two kinds of metal targets, that is, a Ta target and a Pd target are used, and a compound containing Ta and Pd. Includes using any target.
The use of two types of metal targets is convenient for adjusting the constituent components of TaPdN. When two types of metal targets are used, the constituent components of the TaPdN film can be adjusted by adjusting the input power to the target. On the other hand, when using a compound target, it is preferable to adjust the target composition in advance so that the TaPdN film to be formed has a desired composition.
The conditions for forming the TaPdN film will be described below, taking as an example the case where the inert gas atmosphere contains Ar and N ₂ .
Conditions for forming TaPdN film Sputtering gas: Ar and N ₂ mixed gas (Ar gas concentration 97 to 20 vol%, N ₂ gas concentration 3 to 80 vol%, gas pressure 0.5 × 10 ⁻¹ Pa to ¹ . 0 Pa)
Input power: 30 to 1000 W, preferably 50 to 750 W, more preferably 70 to 500 W
Deposition rate: 0.0083 to 1 nm / sec, preferably 0.017 to 0.75 nm / sec, more preferably 0.025 to 0.5 nm / sec
In the above description, the sputtering gas is a mixed gas of Ar and N _2. However, as the sputtering gas, a mixed gas of an inert gas other than Ar and N ₂ or a mixed gas of a plurality of inert gases N ₂ is used. When used, the total concentration of the inert gas is set to the same concentration range as the Ar gas concentration described above.

The EUV mask blank 1 of the present invention has a mask pattern on the absorption layer 14 in addition to the configuration shown in FIG. 1, that is, the substrate 11, the reflective layer 12, the protective layer 13, and the absorption layer 14 (upper layer 14a and lower layer 14b). A low reflection layer for inspection light used for the inspection may be formed.

  The low reflection layer is formed of a film that exhibits low reflection in the inspection light used for inspection of the mask pattern. When producing an EUV mask, after forming a pattern in the absorption layer, it is inspected whether this pattern is formed as designed. In this mask pattern inspection, an inspection machine that normally uses light of about 257 nm as inspection light is used. That is, the difference in reflectance of light of about 257 nm, specifically, the reflectance between the surface exposed by removing the absorption layer by pattern formation and the surface of the absorption layer remaining without removal by pattern formation. Inspected by difference. Here, the former is a reflective layer surface or a protective layer surface, and is usually a protective layer surface. Therefore, if the difference in reflectance between the reflection layer surface or the protective layer surface and the absorption layer surface with respect to the wavelength of the inspection light is small, the contrast at the time of inspection deteriorates and accurate inspection cannot be performed.

The absorption layer composed of a Cr-based film and a TaPd-based film has extremely low EUV reflectivity and has excellent characteristics as an absorption layer for an EUV mask blank. Is not necessarily low enough. As a result, the difference between the reflectance of the absorption layer surface at the wavelength of the inspection light and the reflectance of the reflection layer surface or the protective layer surface becomes small, and there is a possibility that sufficient contrast at the time of inspection cannot be obtained. If sufficient contrast at the time of inspection is not obtained, pattern defects cannot be sufficiently determined in mask inspection, and accurate defect inspection cannot be performed.
If a low reflection layer for inspection light is formed on the absorption layer, the reflectance at the wavelength of the inspection light becomes extremely low, and the contrast at the time of inspection becomes good. When a low reflection layer is formed on the absorption layer, the low reflection layer has a maximum reflectance of a wavelength of 15% or less when the surface of the low reflection layer is irradiated with light in the wavelength region of the inspection light. Is preferably 10% or less, more preferably 5% or less.
If the reflectance of the wavelength of the inspection light in the low reflection layer is 15% or less, the contrast during the inspection is good. Specifically, the contrast between the reflected light with the wavelength of the inspection light on the surface of the reflective layer or the protective layer and the reflected light with the wavelength of the inspection light on the surface of the low reflective layer is 30% or more.

In this specification, the contrast can be obtained using the following equation.
Contrast (%) = ((R ₂ −R ₁ ) / (R ₂ + R ₁ )) × 100
Here, R _{2 at} the wavelength of the inspection light is a reflectance on the surface of the reflective layer or the protective layer, and R ₁ is a reflectance on the surface of the low reflective layer. The R ₁ and R ₂ are measured in a state where a pattern is formed on the absorption layer (and the low reflection layer) of the EUV mask blank. The R ₂ is a value measured on the surface of the reflective layer or the protective layer exposed to the outside after the absorption layer and the low reflection layer are removed by pattern formation, and R ₁ is the low reflection remaining without being removed by the pattern formation. It is the value measured on the surface of the layer.
When the EUV mask blank of the present invention has a low reflection layer, the contrast represented by the above formula is more preferably 45% or more, further preferably 60% or more, and particularly preferably 80% or more.

In order to achieve the above characteristics, the low reflection layer is preferably made of a material whose refractive index at the wavelength of the inspection light is lower than that of the absorption layer, and its crystalline state is amorphous.
The low reflection layer satisfying this characteristic includes at least one selected from the group consisting of tantalum (Ta), palladium (Pd), chromium (Cr), silicon (Si), and hafnium (Hf), oxygen (O), and nitrogen. And at least one selected from the group consisting of (N). Preferable examples of such a low reflection layer include TaPdO layer, TaPdON layer, TaON layer, CrO layer, CrON layer, SiON layer, SiN layer, HfO layer, and HfON layer.
The total content of Ta, Pd, Cr, Si, and Hf in the low reflection layer is preferably 10 to 55 at%, particularly 10 to 50 at%, because the optical characteristics with respect to the wavelength region of the pattern inspection light can be controlled. .
Further, it is preferable that the total content of O and N in the low reflection layer is 45 to 90 at%, particularly 50 to 90 at%, because the optical characteristics with respect to the wavelength region of the pattern inspection light can be controlled. The total content of Ta, Pd, Cr, Si, Hf, O and N in the low reflective layer is preferably 95 to 100 at%, more preferably 97 to 100 at%, and further preferably 99 to 100 at%.

The low reflective layer having the above composition has an amorphous crystal state and excellent surface smoothness. Specifically, the surface roughness (rms) of the surface of the low reflection layer is 0.5 nm or less.
As described above, the surface of the absorption layer is required to be smooth in order to prevent deterioration of the dimensional accuracy of the pattern due to the influence of edge roughness. Since the low reflection layer is formed on the absorption layer, the surface thereof is required to be smooth for the same reason.
If the surface roughness of the low reflective layer surface (rms) is 0.5nm or less, the low reflective layer table surface is sufficiently smooth, the dimensional precision of a pattern due to the influence of the edge roughness will not be deteriorated. The surface roughness (rms) of the low reflective layer surface is more preferably 0.4 nm or less, and further preferably 0.3 nm or less.
In terms of reducing the surface roughness, it is preferable to contain N in the low reflection layer.

  It should be noted that the crystal state of the low reflection layer is amorphous, that is, the amorphous structure or the microcrystalline structure is the same as the evaluation of the crystal state in the absorption layer described above, X-ray diffraction (XRD). It can be confirmed by law. If the crystal state of the low reflection layer is an amorphous structure or a microcrystalline structure, a sharp peak is not observed in a diffraction peak obtained by XRD measurement.

  When forming a low reflection layer on an absorption layer, the film thickness of a low reflection layer can be arbitrarily set in the range which satisfies the above-mentioned conditions, ie, (1)-(5).

The low reflection layer having the above-described configuration can be formed by performing a sputtering method using a target containing at least one of Ta, Pd, Cr, Si, and Hf. Here, as the target, any of the above-described two or more kinds of metal targets and compound targets can be used.
The use of two or more types of metal targets is convenient for adjusting the constituent components of the low reflection layer. In addition, when using 2 or more types of metal targets, the structural component of an absorption layer can be adjusted by adjusting the input electric power to a target. On the other hand, when using a compound target, it is preferable to adjust the target composition in advance so that the formed low reflection layer has a desired composition.

The sputtering method using the above target can be carried out in an inert gas atmosphere in the same manner as the sputtering method for forming the absorption layer.
However, when the low reflection layer contains O, the sputtering method is performed in an inert gas atmosphere containing at least one of He, Ar, Ne, Kr, and Xe and O ₂ . When the low reflective layer contains N, the sputtering method is performed in an inert gas atmosphere containing at least one of He, Ar, Ne, Kr, and Xe and N ₂ . When the low reflective layer contains O and N, the sputtering method is performed in an inert gas atmosphere containing at least one of He, Ar, Ne, Kr and Xe, and O ₂ and N ₂ .

Specific conditions for performing the sputtering method vary depending on the target to be used and the composition of the inert gas atmosphere in which the sputtering method is performed. In any case, the sputtering method may be performed under the following conditions.
The conditions for forming the low reflective layer are shown below, taking as an example the case where the inert gas atmosphere is a mixed gas atmosphere of Ar and O ₂ .
Forming conditions <br/> gas pressure of the low reflective ^{layer: 1.0 × 10 -1 Pa~50 × 10} -1 Pa, preferably ^{1.0 × 10 -1 Pa~40 × 10 -1} Pa, more preferably 1.0 × 10 ⁻¹ Pa to 30 × 10 ⁻¹ Pa.
Sputtering gas: Ar and O ₂ mixed gas (O ₂ gas concentration: 3 to 80 vol%, preferably 5 to 60 vol%, more preferably 10 to 40 vol%).
Input power: 30 to 1000 W, preferably 50 to 750 W, more preferably 80 to 500 W
Deposition rate: 0.01 to 60 nm / min, preferably 0.05 to 45 nm / min, more preferably 0.1 to 30 nm / min
When using an inert gas other than Ar or a plurality of inert gases, the total concentration of the inert gas is set to the same concentration range as the Ar gas concentration described above. Further, the inert gas atmosphere when containing N ₂ if N ₂ concentration, inert gas atmosphere containing N ₂ and O _2, the same concentration range as the oxygen concentrations above the total concentration.

  In the EUV mask blank of the present invention, the low reflection layer is preferably formed on the absorption layer because the wavelength of the pattern inspection light and the wavelength of the EUV light are different. Therefore, when EUV light (near 13.5 nm) is used as pattern inspection light, it is considered unnecessary to form a low reflection layer on the absorption layer. The wavelength of the inspection light tends to shift to the short wavelength side as the pattern size becomes smaller, and it is conceivable that it will shift to 193 nm and further to 13.5 nm in the future. When the wavelength of the inspection light is 13.5 nm, it is considered unnecessary to form a low reflection layer on the absorption layer.

  However, when the low reflection layer is not formed on the absorption layer, a surface protective layer described later may be provided on the absorption layer in order to improve the cleaning resistance in the cleaning step performed in the process of manufacturing the EUV mask. In the cleaning process performed in the EUV mask manufacturing process, the EUV mask blank surface is cleaned with an acidic solution containing sulfuric acid or the like. When the low reflection layer is not formed on the absorption layer, the surface of the EUV mask blank is the surface of the absorption layer. In the case of the EUV mask blank of the present invention, the surface of the upper layer 14a of the absorption layer 14 is the outermost layer. Depending on the material of the upper layer 14a and the cleaning conditions using an acidic solution (for example, cleaning conditions including high-concentration acidic solution cleaning or excessive repeated cleaning), the film constituting the upper layer 14a may be noticeably eroded. . Among the films constituting the upper layer 14a exemplified above, the CrN film and the TaPdN film may be noticeably eroded by the acidic solution depending on the cleaning conditions. If the film thickness of the upper layer 14a is greatly reduced, the reflectance of EUV light and the phase difference with the reflective layer may change with respect to the design value.

In the EUV mask blank of the present invention, when the upper layer 14a of the absorption layer 14 is a CrN film or a TaPdN film and a low reflection layer is not formed on the absorption layer 14, a cleaning process is performed on the CrN film or the TaPdN film. In this case, a surface protective layer for protecting the CrN film or the TaPdN film may be formed.
4 and 5 are schematic cross-sectional views showing an EUV mask blank having a surface protective layer formed thereon. In the EUV mask blank 1 shown in FIG. 4, the upper layer 14a of the absorption layer 14 has a two-layer structure of a TaPdN film 14a1 and a surface protective layer 14a2 formed on the TaPdN film 14a1. In the mask blank 1 shown in FIG. 4, the lower layer 14b of the absorption layer 14 is a Cr-based film.
FIG. 5 is a schematic cross-sectional view showing another embodiment of an EUV mask blank having a surface protective layer formed thereon. In the EUV mask blank 1 shown in FIG. 5, the upper layer 14a of the absorption layer 14 has a two-layer structure of a CrN film 14a1 and a surface protective layer 14a2 formed on the CrN film 14a1. In the mask blank 1 shown in FIG. 5, the lower layer 14b of the absorption layer 14 is a TaPd-based film.

In the EUV mask blank 1 shown in FIG. 4, the surface protective layer 14a2 formed on the TaPdN film 14a1 contains Ta, Pd and O, and the TaPdO film having an O content of 30 to 85 at%, or Ta, Pd , O and N, the total content of O and N is 40 to 90 at%, and the composition ratio of O and N is O: N = 9: 1 to 6: 4.
When the surface protective layer 14a2 is a TaPdO film, if the O content is less than 30 at%, the TaPdO film is easily eroded by the acidic solution used for cleaning, and thus the function as the surface protective layer cannot be sufficiently exhibited. On the other hand, when the O content of the TaPdO film exceeds 85 at%, there is a problem that the discharge becomes unstable during film formation. The TaPdO film as the surface protective layer 14a2 has an O content of preferably 35 to 85 at%, more preferably 40 to 85 at%.
The TaPdO film as the surface protective layer 14a2 has a total content of Ta and Pd of 15 to 70 at % , preferably 15 to 65 at%, and more preferably 15 to 60 at%.
The TaPdO film as the surface protective layer 14a2 may have a Ta content of 7 to 32 at%, a Pd content of 8 to 38 at%, a Ta content of 7 to 30 at%, and a Pd content of If it is 8-35 at%, it is preferable, Ta content rate is 7-27 at%, and if Pd content rate is 8-33 at%, it is more preferable.

When the surface protective layer 14a2 is a TaPdON film, if the total content of O and N is less than 40 at%, the TaPdON film is easily eroded by the acidic solution used for cleaning, and thus the function as the surface protective layer cannot be sufficiently exhibited. On the other hand, when the total content of O and N in the TaPdON film exceeds 90 at%, there is a problem that the discharge becomes unstable during the film formation. When O of the TaPdON film is lower than the above composition ratio, the TaPdON film is easily eroded by the acidic solution used for cleaning, and thus the function as the surface protective layer cannot be sufficiently exhibited. On the other hand, when O of the TaPdON film is higher than the above composition ratio, there are problems such as unstable discharge during film formation.
The TaPdON film as the surface protective layer 14a2 has a total content of O and N of preferably 40 to 85 at%, more preferably 40 to 80 at%. The composition ratio of O and N is preferably O: N = 9: 1 to 6.5: 3.5, and more preferably O: N = 9: 1 to 7: 3.
The TaPdON film as the surface protective layer 14a2 has a total content of Ta and Pd of 10 to 60 at % , preferably 15 to 60 at%, and more preferably 20 to 60 at%.
The TaPdON film as the surface protective layer 14a2 may have a Ta content of 5 to 27 at%, a Pd content of 5 to 33 at%, a Ta content of 7 to 27 at%, and a Pd content of If it is 8-33 at%, Ta content is 9-27 at%, and if Pd content is 11-33 at%, it is more preferable.

  In the EUV mask blank 1 shown in FIG. 5, the surface protective layer 14a2 formed on the CrN film 14a1 contains Cr and O, the Cr content is 15 to 70 at%, and the O content is 30 to 85 at%. Or Cr, O, and N, the Cr content is 10 to 60 at%, the total content of O and N is 40 to 90 at%, and the composition ratio of O and N is O : N = 9: 1 to 6: 4 CrON film.

When the surface protective layer 14a2 is a CrO film, if the O content is less than 30 at%, the CrO film is easily eroded by the acidic solution used for cleaning, and thus the function as the surface protective layer cannot be sufficiently exhibited. On the other hand, if the O content of the CrO film exceeds 85 at%, there is a problem that the discharge becomes unstable during film formation.
The CrO film as the surface protective layer 14a2 has a Cr content of preferably 15 to 65 at%, more preferably 15 to 60 at%. The O content is preferably 35 to 85 at%, more preferably 40 to 85 at%.

When the surface protective layer 14a2 is a CrON film, if the total content of O and N is less than 40 at%, the CrON film is easily eroded by the acidic solution used for cleaning, so that the function as the surface protective layer cannot be sufficiently exhibited. On the other hand, when the total content of O and N in the CrON film exceeds 90 at%, there is a problem that the discharge becomes unstable during film formation. When the O of the CrON film is lower than the above composition ratio, the CrON film is easily eroded by the acidic solution used for cleaning, so that the function as the surface protective layer cannot be sufficiently exhibited. On the other hand, when O of the CrON film is higher than the above composition ratio, there are problems such as unstable discharge during film formation.
The CrON film as the surface protective layer 14a2 has a Cr content of preferably 15 to 60 at%, more preferably 20 to 60 at%. The total content of O and N is preferably 40 to 85 at%, more preferably 40 to 80 at%. The composition ratio of O and N is preferably O: N = 9: 1 to 6.5: 3.5, and more preferably O: N = 9: 1 to 7: 3.

  In any case of the EUV mask blank 1 shown in FIGS. 4 and 5, the crystal state of the surface protective layer 14a2 is preferably amorphous. That is, it is preferable that the CrO film, the CrON film, the TaPdO film, and the TaPdON film as the surface protective layer 14a2 have an amorphous crystal state. If these film crystal states are amorphous, the surface of the absorption layer 14 is excellent in smoothness, and the surface roughness (rms) of the surface of the absorption layer 14 described above can be achieved.

  In any case of the EUV mask blank 1 shown in FIGS. 4 and 5, the surface protective layer 14 a 2 may further contain H, Si, and B. That is, any of the CrO film, CrON film, TaPdO film, and TaPdON film as the surface protective layer 14a2 may further contain H, Si, and B. When these films contain H, Si, and B, the total content of these films can be 0.1 to 10 at%, particularly 0.1 to 5 at%. It is preferable because it contributes to smoothing the surface.

  In any case of the EUV mask blank 1 shown in FIGS. 4 and 5, the Cr constituting the upper layer 14a and the lower layer 14b including the CrO film, the CrON film, the TaPdO film, and the TaPdON film as the surface protective layer 14a2. The total film stress of the system film and the TaPd system film is achieved.

In any case of the EUV mask blank shown in FIGS. 4 and 5, the thickness of the surface protective layer 14a2 is preferably 0.5 nm or more and 5 nm or less. If the thickness of the surface protective layer 14a2 is 0.5 nm or more, the function as the surface protective layer can be sufficiently exhibited. On the other hand, if the film thickness of the surface protective layer 14a2 is larger than 5 nm, the increase in the film thickness no longer contributes to the improvement of the function as the surface protective layer, and the time required for forming the surface protective layer 14a2 increases. The cost required for forming the layer 14a2 increases. Further, since the surface protective layer 14a2 is a film containing oxygen, arcing (abnormal discharge) is likely to occur during film formation, and the risk of generating particles increases.
Further, the thickness of the surface protective layer 14a2 is more preferably 1 to 5 nm, and further preferably 1.5 to 5 nm.

  In any case of the EUV mask blank 1 shown in FIGS. 4 and 5, the conditions (1) to (5) relating to the absorption layer 14 of the EUV mask blank of the present invention described above are satisfied. Therefore, the total film thickness (L) of the absorption layer 14 is 30 nm or more and 45 nm or less including the film thickness of the surface protective layer 14a2. In the case of the EUV mask blank 1 shown in FIG. 4, the total thickness of the TaPdN film 14a1 and the TaPdO film or TaPdON film as the surface protective layer 14a2 is 8 nm or more and 36 nm or less. On the other hand, in the case of the EUV mask blank 1 shown in FIG. 5, the film thickness of the CrN film 14a1 is 11 nm or more and 36 nm or less.

  In any case of the EUV mask blank 1 shown in FIGS. 4 and 5, the CrO film, the CrON film, the TaPdO film, and the TaPdON film as the surface protective layer 14a2 are subjected to a known film forming method, for example, a sputtering method. Can be formed.

When the surface protective layer 14a2 is a CrO film, a sputtering method such as magnetron is used in an inert gas atmosphere containing at least one of He, Ar, Ne, Kr, and Xe and O ₂ using a Cr target. A sputtering method or an ion beam sputtering method may be performed. The conditions for forming the CrO film will be described below, taking as an example the case where the inert gas atmosphere is an atmosphere containing Ar and O ₂ .
Forming conditions <br/> gas pressure CrO ^{film: 1.0 × 10 -1 Pa~50 × 10} -1 Pa, preferably ^{1.0 × 10 -1 Pa~40 × 10 -1} Pa, more preferably 1 ^{.0 × 10 -1 Pa~30 × 10 -1} Pa.
Sputtering gas: Ar and O ₂ mixed gas (O ₂ gas concentration 3 to 80 vol%, preferably 5 to 60 vol%, more preferably 10 to 40 vol%).
Input power: 30 to 1000 W, preferably 50 to 750 W, more preferably 80 to 500 W
Deposition rate: 0.00017-1 nm / sec, preferably 0.00083-0.75 nm / sec, more preferably 0.0017-0.5 nm / sec
In the above description, the sputtering gas is a mixed gas of Ar and O _2. However, as the sputtering gas, a mixed gas of an inert gas other than Ar and O ₂ , or a mixed gas of a plurality of inert gases and O ₂ is used. Is used, the total concentration of the inert gas is set to the same concentration range as the Ar gas concentration described above. The same applies to the formation conditions of other films described below.

When the surface protective layer 14a2 is a CrON film, using a Cr target, a sputtering method, for example, in an inert gas atmosphere containing at least one of He, Ar, Ne, Kr, and Xe and O ₂ and N ₂ , for example, A magnetron sputtering method or an ion beam sputtering method may be performed. The conditions for forming the CrON film will be described below, taking as an example the case where the inert gas atmosphere is an atmosphere containing Ar, O ₂ and N ₂ .
Forming conditions <br/> gas pressure CrON ^{film: 1.0 × 10 -1 Pa~50 × 10} -1 Pa, preferably ^{1.0 × 10 -1 Pa~40 × 10 -1} Pa, more preferably 1 ^{.0 × 10 -1 Pa~30 × 10 -1} Pa.
Sputtering gas: Mixed gas of Ar, O ₂ and N ₂ (O ₂ gas concentration 5 to 80 vol%, N ₂ gas concentration 5 to 75 vol%, preferably O ₂ gas concentration 6 to 70 vol%, N ₂ gas concentration 6 to 35 vol) %, more preferably O ₂ gas concentration 10 to 30 vol%, N ₂ gas concentration 10 to 30 vol% .Ar gas concentration 5～90Vol%, preferably 10～88Vol%, more preferably 20~80vol%).
Input power: 30 to 1000 W, preferably 50 to 750 W, more preferably 80 to 500 W
Deposition rate: 0.00017-1 nm / sec, preferably 0.00083-0.75 nm / sec, more preferably 0.0017-0.5 nm / sec

When the surface protective layer 14a2 is a TaPdO film, using a target containing Ta and Pd, in an inert gas atmosphere containing at least one of He, Ar, Ne, Kr, and Xe and O ₂ A sputtering method such as a magnetron sputtering method or an ion beam sputtering method may be performed.
In this specification, when using a target containing Ta and Pd, two types of metal targets, that is, a Ta target and a Pd target, and Ta and Pd are used. Includes any of using compound targets that include.
The use of two types of metal targets is convenient for adjusting the constituent components of TaPdO. When two types of metal targets are used, the constituent components of the TaPdO film can be adjusted by adjusting the input power to the target. On the other hand, when using a compound target, it is preferable to adjust the target composition in advance so that the formed TaPdO film has a desired composition.
The conditions for forming the TaPdO film will be described below, taking as an example the case where the inert gas atmosphere contains Ar and O ₂ .
Forming conditions <br/> gas pressure TaPdO ^{membrane: 1.0 × 10 -1 Pa~50 × 10} -1 Pa, preferably ^{1.0 × 10 -1 Pa~40 × 10 -1} Pa, more preferably 1 ^{.0 × 10 -1 Pa~30 × 10 -1} Pa.
Sputtering gas: Ar and O ₂ mixed gas (O ₂ gas concentration 3 to 80 vol%, preferably 5 to 60 vol%, more preferably 10 to 40 vol%).
Input power: 30 to 1000 W, preferably 50 to 750 W, more preferably 80 to 500 W
Deposition rate: 0.00017-1 nm / sec, preferably 0.00083-0.75 nm / sec, more preferably 0.0017-0.5 nm / sec

When the surface protective layer 14a2 is a TaPdON film, using a target containing Ta and Pd, in an inert gas atmosphere containing at least one of He, Ar, Ne, Kr, and Xe, and O ₂ and N ₂ Then, a sputtering method, for example, a magnetron sputtering method or an ion beam sputtering method may be performed. The conditions for forming the TaPdON film are shown below, taking as an example the case where the inert gas atmosphere is an atmosphere containing Ar, O ₂ and N ₂ .
Forming conditions <br/> gas pressure TaPdON ^{film: 1.0 × 10 -1 Pa~50 × 10} -1 Pa, preferably ^{1.0 × 10 -1 Pa~40 × 10 -1} Pa, more preferably 1 ^{.0 × 10 -1 Pa~30 × 10 -1} Pa.
Sputtering gas: Mixed gas of Ar, O ₂ and N ₂ (O ₂ gas concentration 5 to 80 vol%, N ₂ gas concentration 5 to 75 vol%, preferably O ₂ gas concentration 6 to 70 vol%, N ₂ gas concentration 6 to 35 vol) %, more preferably O ₂ gas concentration 10 to 30 vol%, N ₂ gas concentration 10 to 30 vol% .Ar gas concentration 5～90Vol%, preferably 10～88Vol%, more preferably 20~80vol%).
Input power: 30 to 1000 W, preferably 50 to 750 W, more preferably 80 to 500 W
Deposition rate: 0.00017-1 nm / sec, preferably 0.00083-0.75 nm / sec, more preferably 0.0017-0.5 nm / sec

  In the EUV mask blank of the present invention, on the absorption layer (when the low reflection layer is formed on the absorption layer, on the absorption layer), it is described in JP2009-54899A or JP2009-21582A. A hard mask layer, that is, a layer of a material resistant to the etching conditions of the absorption layer (or the absorption layer and the low reflection layer when the low reflection layer is formed on the absorption layer) may be formed. . By forming such a hard mask layer, the absorption layer (the low reflection layer is formed on the absorption layer) under the etching conditions of the absorption layer (the absorption layer and the low reflection layer when the low reflection layer is formed on the absorption layer) is formed. If formed, the etching selectivity between the absorption layer and the low reflection layer) and the hard mask layer, specifically, the absorption layer (if the low reflection layer is formed on the absorption layer, the absorption layer and the low reflection layer) The ratio of the etching rate of the absorption layer under the etching conditions of the layer) (the etching rate of the absorption layer and the low reflection layer when a low reflection layer is formed on the absorption layer) and the etching rate of the hard mask layer By increasing the thickness, the resist can be thinned.

Moreover, the EUV mask blank of this invention may have a well-known functional film in the field of EUV mask blank other than said structure. As a specific example of such a functional film, for example, as described in JP-A-2003-501823, a high dielectric applied to the back side of the substrate in order to promote electrostatic chucking of the substrate. A functional coating. Here, the back surface of the substrate refers to the surface of the substrate 11 in FIG. 1 opposite to the side on which the reflective layer 12 is formed. For the high dielectric coating applied to the back surface of the substrate for such a purpose, the electrical conductivity and thickness of the constituent material are selected so that the sheet resistance is 100Ω / □ or less. The constituent material of the high dielectric coating can be widely selected from those described in known literature. For example, a high dielectric constant coating described in JP-A-2003-501823, specifically, a coating made of silicon, TiN, molybdenum, chromium, and TaSi can be applied. The thickness of the high dielectric coating can be 10 to 1000 nm, for example.
The high dielectric coating can be formed using a known film forming method, for example, a sputtering method such as a magnetron sputtering method or an ion beam sputtering method, a CVD method, a vacuum evaporation method, or an electrolytic plating method.

The present invention will be further described below using examples.
Example 1
In this example, the EUV mask blank 1 shown in FIG. 1 was produced.
As the substrate 11 for film formation, a SiO ₂ —TiO ₂ glass substrate (outer dimensions 6 inches (152 mm) square, thickness 6.3 mm) was used. This glass substrate has a thermal expansion coefficient at 20 ° C. of 0.05 × 10 ⁻⁷ / ° C., Young's modulus of 67 GPa, Poisson's ratio of 0.17, and specific rigidity of 3.07 × 10 ⁷ m ² / s ² . This glass substrate was polished to form a smooth surface with a surface roughness (rms) of 0.15 nm or less and a flatness of 100 nm or less.

A high dielectric coating having a sheet resistance of 100Ω / □ was applied to the back side of the substrate 11 by depositing a Cr film having a thickness of 100 nm using a magnetron sputtering method.
A substrate 11 (outer diameter 6 inches (152 mm) square, thickness 6.3 mm) is fixed to a flat electrostatic chuck having a flat plate shape by using the formed Cr film, and ion beam sputtering is performed on the surface of the substrate 11. The Mo / Si multilayer reflective film (reflective layer 12) having a total film thickness of 272 nm ((4.5 nm + 2.3 nm) × 40) is obtained by repeating 40 cycles of alternately forming the Si film and the Mo film using the method. Formed.
Furthermore, the protective layer 13 was formed by forming a Ru film (film thickness: 2.5 nm) on the Mo / Si multilayer reflective film (reflective layer 12) using an ion beam sputtering method.

The deposition conditions for the Si film, the Mo film, and the Ru film are as follows.
Conditions for forming the Si film Target: Si target (boron doped)
Sputtering gas: Ar gas (gas pressure 0.02 Pa)
Voltage: 700V
Deposition rate: 0.077 nm / sec
Film thickness: 4.5nm
Conditions for forming the Mo film Target: Mo target Sputtering gas: Ar gas (gas pressure 0.02 Pa)
Voltage: 700V
Deposition rate: 0.064 nm / sec
Film thickness: 2.3 nm
Ru film formation conditions Target: Ru target Sputtering gas: Ar gas (gas pressure 0.02 Pa)
Voltage: 500V
Deposition rate: 0.023 nm / sec
Film thickness: 2.5nm

Next, a CrN film was formed as a lower layer 14b of the absorption layer 14 on the protective layer 13 by using a magnetron sputtering method.
The film formation conditions for the lower layer 14b (CrN film) are as follows.
Deposition conditions <br/> target lower 14b (CrN film): Cr target Sputtering gas: mixed gas of Ar and _{N 2 (Ar: 58.2vol%,} N 2: 41.8vol%, gas pressure: 0.1 Pa )
Input power: 1500W
Deposition rate: 0.18 nm / sec
Film thickness: 16nm
The formed film composition includes an X-ray Photoelectron Spectrometer (manufactured by PERKIN ELEMER-PHI), a secondary ion mass spectrometer (Secondary Ion Mass Spectrometer) (manufactured by PHI-ATOMIKA), and Rutherford backscattering. The measurement is performed using a spectroscopic device (Rutherford Back Scattering Spectroscopy) (manufactured by Kobe Steel). The composition ratio (at%) of the lower layer 14b (CrN film) was Cr: N = 86.0: 14.0.

Next, a TaPdN film was formed as the upper layer 14a of the absorption layer 14 on the lower layer 14b (CrN film) by using a magnetron sputtering method. The film formation conditions for the upper layer 14a (TaPdN film) are as follows.
Deposition conditions <br/> target layer 14a (TaPdN film): Ta target and Pd target sputtering gas: Ar and N ₂ mixed gas _{(Ar: 86vol%, N 2} : 14vol%, gas pressure: 0.3 Pa)
Input power: Ta target = 150 W, Pd target = 75 W
Deposition rate: 0.32 nm / sec
Film thickness: 16nm
The formed film composition is measured by the same method as that for the upper layer 14a. The composition of the upper layer 14a (TaPdN film) is Ta: Pd: N = 41: 25: 34.

The total film thickness (L) of the absorption layer 14 is 32 nm. The EUV light reflection characteristics of this EUV mask blank were evaluated by the following procedure.
In the above film configuration, the EUV reflectance on the surface of the absorption layer 14 and the phase difference (φ) between the surface of the protective layer 13 and the surface of the absorption layer 14 were obtained by calculation. Furthermore, regarding the gradient (Δφ / ΔL) of the phase difference change (Δφ) with respect to the film thickness change (ΔL), the phase difference change (Δφ) in the film thickness range in which the phase difference φ is 180 ° ± 10 °. Calculated by calculating. The results are as follows.
Peak reflectance of EUV light on the surface of the absorption layer 14: 5.6%
Phase difference (φ) between EUV reflected light on the surface of the protective layer 13 and EUV reflected light on the surface of the absorption layer 14: 171.3 °
Gradient (Δφ / ΔL) of change (Δφ) in phase difference (φ) with respect to change (ΔL) in total film thickness (L) of absorption layer 14: 0.0 deg / nm

Example 2
The same procedure as in Example 1 except that the film thickness of the CrN film as the lower layer 14b is 30 nm, the film thickness of the TaPdN film as the upper layer 14a is 8 nm, and the total film thickness (L) of the absorption layer 14 is 38 nm. Carried out. The reflection characteristics of EUV light are as follows.
Peak reflectance of EUV light on the surface of the absorption layer 14: 5.6%
Phase difference (φ) between EUV reflected light on the surface of the protective layer 13 and EUV reflected light on the surface of the absorption layer 14: 174.0 °
Gradient (Δφ / ΔL) of change (Δφ) in phase difference (φ) with respect to change (ΔL) in total film thickness (L) of absorption layer 14: 9.1 deg / nm

Example 3
The same procedure as in Example 1 except that the film thickness of the CrN film as the lower layer 14b is 5 nm, the film thickness of the TaPdN film as the upper layer 14a is 25 nm, and the total film thickness (L) of the absorption layer 14 is 30 nm. Carried out. The reflection characteristics of EUV light are as follows.
Peak reflectance of EUV light on the surface of the absorption layer 14: 8.5%
Phase difference (φ) between EUV reflected light on the surface of the protective layer 13 and EUV reflected light on the surface of the absorption layer 14: 179.2 °
Gradient (Δφ / ΔL) of change (Δφ) in phase difference (φ) with respect to change (ΔL) in total film thickness (L) of absorption layer 14: 12.9 deg / nm

Example 4
The same procedure as in Example 1 except that the film thickness of the CrN film as the lower layer 14b is 35 nm, the film thickness of the TaPdN film as the upper layer 14a is 9 nm, and the total film thickness (L) of the absorption layer 14 is 44 nm. Carried out. The reflection characteristics of EUV light are as follows.
Peak reflectance of EUV light on the surface of the absorption layer 14: 5.1%
Phase difference (φ) between EUV reflected light on the surface of the protective layer 13 and EUV reflected light on the surface of the absorption layer 14: 186.9 °
Gradient (Δφ / ΔL) of change (Δφ) in phase difference (φ) with respect to change (ΔL) in total film thickness (L) of absorption layer 14: 12.5 deg / nm

Example 5
In this embodiment, the lower layer 14b is a TaPdN film and the upper layer 14a is a CrN film. The conditions for forming the TaPdN film and the CrN film are the same as those in Example 1. The thickness of the TaPdN film as the lower layer 14b was 10 nm, the thickness of the CrN film as the upper layer 14a was 28 nm, and the total thickness (L) of the absorption layer 14 was 38 nm. The reflection characteristics of EUV light are as follows.
Peak reflectance of EUV light on the surface of the absorption layer 14: 5.4%
Phase difference (φ) between EUV reflected light on the surface of the protective layer 13 and EUV reflected light on the surface of the absorption layer 14: 179.5 °
Gradient (Δφ / ΔL) of change (Δφ) in phase difference (φ) with respect to change (ΔL) in total film thickness (L) of absorption layer 14: 9.7 deg / nm

Example 6
The same procedure as in Example 5 except that the thickness of the TaPdN film as the lower layer 14b is 25 nm, the thickness of the CrN film as the upper layer 14a is 6 nm, and the total thickness (L) of the absorption layer 14 is 31 nm. Carried out. The reflection characteristics of EUV light are as follows.
Peak reflectance of EUV light on the surface of the absorption layer 14: 7.5%
Phase difference (φ) between EUV reflected light on the surface of the protective layer 13 and EUV reflected light on the surface of the absorption layer 14: 181.2 °
Gradient (Δφ / ΔL) of change (Δφ) in phase difference (φ) with respect to change (ΔL) in total film thickness (L) of absorption layer 14: 10.2 deg / nm

Example 7
The same procedure as in Example 1 except that the film thickness of the CrN film as the lower layer 14b is 2 nm, the film thickness of the TaPdN film as the upper layer 14a is 36 nm, and the total film thickness (L) of the absorption layer 14 is 38 nm. Carried out. The reflection characteristics of EUV light are as follows.
Peak reflectance of EUV light on the surface of the absorption layer 14: 5.4%
Phase difference (φ) between EUV reflected light on the surface of the protective layer 13 and EUV reflected light on the surface of the absorption layer 14: 181.2 °
Gradient (Δφ / ΔL) of change (Δφ) in phase difference (φ) with respect to change (ΔL) in total film thickness (L) of absorption layer 14: 12.1 deg / nm

Example 8
In this embodiment, as shown in the EUV mask blank 1 shown in FIG. 4, the thickness of the CrN film as the lower layer 14b is 2 nm, the upper layer 14a is the TaPdN film 14a1, and the surface protection formed on the TaPdN film 14a1. The same procedure as in Example 7 was performed, except that the TaPdN film 14a1 was 33 nm thick and the surface protective layer 14a2 was a 3 nm thick TaPdO film formed by the following procedure. The total film thickness (L) of the absorption layer 14 is 38 nm.
Deposition conditions <br/> target surface protective layer 14a2 (TaPdO film): Ta target and Pd target sputtering gas: Ar and O ₂ mixed gas _{(Ar: 86vol%, O 2} : 14vol%, gas pressure: 0.3 Pa )
Input power: Ta target = 150 W, Pd target = 150 W
Deposition rate: 0.18 nm / sec
Film thickness: 3nm
The formed film composition is measured by the same method as the upper layer 14a of Example 1. The composition of the surface protective layer 14a2 (TaPdO film) is Ta: Pd: O = 27: 32: 41.
The reflection characteristics of EUV light are as follows.
Peak reflectance of EUV light on the surface of the absorption layer 14: 5.3%
Phase difference (φ) between EUV reflected light on the surface of the protective layer 13 and EUV reflected light on the surface of the absorption layer 14: 180.3 °
Gradient (Δφ / ΔL) of change (Δφ) in phase difference (φ) with respect to change (ΔL) in total film thickness (L) of absorption layer 14: 11.5 deg / nm
About the present Example, washing | cleaning resistance evaluation was implemented in the following procedure.
(Evaluation of washing resistance)
A TaPdO film was formed on a quartz glass substrate in the same procedure as the formation of the surface protective layer 14a2, and a sample for evaluation of cleaning resistance was produced. For comparison, a sample in which a TaPdN film was formed on a quartz glass substrate was prepared in the same procedure as the formation of the upper layer 14a (TaPdN film) in Example 1. However, the thickness of the TaPdN film of this sample was 4 nm.
The sample was repeatedly washed for 3 minutes in an acidic solution containing sulfuric acid 5 times, and the change in film thickness before and after the washing was measured using XRR (X-Ray Reflection: manufactured by Rigaku Corporation).
In the case of the TaPdO film, the change in film thickness after repeated washing 5 times was 0.1 nm or less. On the other hand, in the case of the TaPdN film, the change in film thickness after repeated washing 5 times was 1.1 nm.

Example 9
In this example, the same procedure as in Example 8 is performed except that the surface protective layer 14 a 2 is a TaPdON film. That is, the thickness of the CrN film as the lower layer 14b and 2 nm, and the upper layer 14 a, the TaPdN film 14a1 and 33 nm, the TaPdON film as a surface protective layer 14a2 and 3 nm, the total thickness (L of the absorbent layer 14 ) To 38 nm. The TaPdON film as the surface protective layer 14a2 is formed by the following procedure.
Surface protective layer 14a2 deposition conditions <br/> target (TaPdON film): Ta target and Pd target sputtering gas: Ar, O ₂ and N ₂ mixture gas _{(Ar: 72vol%, O 2} : 14vol%, N 2: 14vol%, gas pressure: 0.3Pa)
Input power: Ta target = 150 W, Pd target = 150 W
Deposition rate: 0.20 nm / sec
Film thickness: 3nm
The formed film composition is measured by the same method as the upper layer 14a of Example 1. The composition of the surface protective layer 14a2 (TaPdON film) is Ta: Pd: O: N = 21: 26: 40: 13.
The reflection characteristics of EUV light are as follows.
Peak reflectance of EUV light on the surface of the absorption layer 14: 5.1%
Phase difference (φ) between EUV reflected light on the surface of the protective layer 13 and EUV reflected light on the surface of the absorption layer 14: 175.9 °
Gradient (Δφ / ΔL) of change (Δφ) in phase difference (φ) with respect to change (ΔL) in total film thickness (L) of absorption layer 14: 10.1 deg / nm
Moreover, as a result of evaluating the washing resistance in the same manner as in Example 8, the change in film thickness after repeated washing 5 times is 0.2 nm or less.

Comparative Example 1
In this comparative example, the absorption layer 14 is a single layer of TaPdN film. The conditions for forming the TaPdN film are the same as in Example 1. The film thickness of the TaPdN film as the absorption layer 14 is 30 nm. The reflection characteristics of EUV light are as follows.
Peak reflectance of EUV light on the surface of the absorption layer 14: 8.3%
Phase difference (φ) between EUV reflected light on the surface of the protective layer 13 and EUV reflected light on the surface of the absorption layer 14: 171.7 °
Gradient (Δφ / ΔL) of change (Δφ) in phase difference (φ) with respect to change (ΔL) in total film thickness (L) of absorption layer 14: 16.0 deg / nm
In this comparative example, Δφ / ΔL was more than 15 deg / nm.

Comparative Example 2
In this comparative example, the absorption layer 14 is a single layer of CrN film. The film forming conditions for the CrN film are the same as in Example 1. The film thickness of the CrN film as the absorption layer 14 is 49 nm. The reflection characteristics of EUV light are as follows.
Peak reflectance of EUV light on the surface of the absorption layer 14: 1.9%
Phase difference (φ) between EUV reflected light on the surface of the protective layer 13 and EUV reflected light on the surface of the absorption layer 14: 174.5 °
Gradient (Δφ / ΔL) of change (Δφ) in phase difference (φ) with respect to change (ΔL) in total film thickness (L) of absorption layer 14: 0.0 deg / nm
In this comparative example, the peak reflectance of EUV light on the surface of the absorption layer 14 was less than 5%.

Comparative Example 3
In this comparative example, the absorption layer 14 is a single layer of CrN film. The film forming conditions for the CrN film are the same as in Example 1. The film thickness of the CrN film as the absorption layer 14 is 44 nm. The reflection characteristics of EUV light are as follows.
Peak reflectance of EUV light on the surface of the absorption layer 14: 4.7%
Phase difference (φ) between EUV reflected light on the surface of the protective layer 13 and EUV reflected light on the surface of the absorption layer 14: 171.2 °
Gradient (Δφ / ΔL) of change (Δφ) in phase difference (φ) with respect to change (ΔL) in total film thickness (L) of absorption layer 14: 13.3 deg / nm
In this comparative example, the peak reflectance of EUV light on the surface of the absorption layer 14 was less than 5%.

Comparative Example 4
In this comparative example, the thickness of the CrN film as the lower layer 14b is 20 nm, the thickness of the TaPdN film as the upper layer 14a is 9 nm, and the total thickness (L) of the absorption layer 14 is 29 nm. The same procedure as 1 was performed. The reflection characteristics of EUV light are as follows.
Peak reflectance of EUV light on the surface of the absorption layer 14: 10.8%
Phase difference (φ) between the EUV reflected light on the surface of the protective layer 13 and the EUV reflected light on the surface of the absorbing layer 14: 126.3 °
Gradient (Δφ / ΔL) of change (Δφ) in phase difference (φ) with respect to change (ΔL) in total film thickness (L) of absorption layer 14: 13.2 deg / nm
In this comparative example in which the total film thickness (L) of the absorption layer 14 was less than 30 nm, φ was out of the range of 180 ° ± 10 °.

Comparative Example 5
In this comparative example, the thickness of the CrN film as the lower layer 14b is 37 nm, the thickness of the TaPdN film as the upper layer 14a is 9 nm, and the total thickness (L) of the absorption layer 14 is 46 nm. The same procedure as 1 was performed. The reflection characteristics of EUV light are as follows.
Peak reflectance of EUV light on the surface of the absorption layer 14: 2.8%
Phase difference (φ) between EUV reflected light on the surface of the protective layer 13 and EUV reflected light on the surface of the absorption layer 14: 218.6 °
Gradient (Δφ / ΔL) of change (Δφ) in phase difference (φ) with respect to change (ΔL) in total film thickness (L) of absorption layer 14: 14.6 deg / nm
In this comparative example in which the total film thickness (L) of the absorption layer 14 exceeds 45 nm, the peak reflectance of EUV light on the surface of the absorption layer 14 is less than 5%, and φ is outside the range of 180 ° ± 10 °. It was.

Comparative Example 6
In this comparative example, the thickness of the CrN film as the lower layer 14b is set to 32 nm, the thickness of the TaPdN film as the upper layer 14a is set to 7 nm, and the total thickness (L) of the absorption layer 14 is set to 39 nm. The same procedure as 1 was performed. The reflection characteristics of EUV light are as follows.
Peak reflectance of EUV light on the surface of the absorption layer 14: 4.2%
Phase difference (φ) between EUV reflected light on the surface of the protective layer 13 and EUV reflected light on the surface of the absorption layer 14: 180.0 °
Gradient (Δφ / ΔL) of change (Δφ) in phase difference (φ) with respect to change (ΔL) in total film thickness (L) of absorption layer 14: 0.0 deg / nm
In this comparative example in which the thickness of the TaPdN film was less than 8 nm, the peak reflectance of EUV light on the surface of the absorption layer 14 was less than 5%.

Comparative Example 7
The same procedure as in Example 5 except that the thickness of the TaPdN film as the lower layer 14b is 32 nm, the thickness of the CrN film as the upper layer 14a is 7 nm, and the total thickness (L) of the absorption layer 14 is 39 nm. Carried out. The reflection characteristics of EUV light are as follows.
Peak reflectance of EUV light on the surface of the absorption layer 14: 3.9%
Phase difference (φ) between EUV reflected light on the surface of the protective layer 13 and EUV reflected light on the surface of the absorption layer 14: 177.7 °
Gradient (Δφ / ΔL) of change (Δφ) in phase difference (φ) with respect to change (ΔL) in total film thickness (L) of absorption layer 14: 0 deg / nm
In this comparative example in which the thickness of the TaPdN film was less than 8 nm, the peak reflectance of EUV light on the surface of the absorption layer 14 was less than 5%.

1: EUV mask blank 11: Substrate 12: Reflective layer (multilayer reflective film)
13: Protective layer 14: Absorbing layer 14a: Upper layer 14a1: CrN film or TaPdN film 14a2: Surface protective layer 14b: Lower layer

Claims (21)

A reflective mask blank for EUV lithography in which a reflective layer for reflecting EUV light and an absorption layer for absorbing EUV light are formed in this order on a substrate,
The absorption layer is composed of a surface side layer (upper layer) and a substrate side layer (lower layer),
One of the upper layer and the lower layer of the absorption layer is a Cr-based film containing chromium (Cr) as a main component and containing at least one of oxygen (O) and nitrogen (N).
The other is a TaPd-based film containing tantalum (Ta) and palladium (Pd) as main components and containing at least one of oxygen (O) and nitrogen (N).
A reflective mask blank for EUV lithography, wherein the absorption layer satisfies the following (1) to (5).
(1) The total film thickness (L) of the absorption layer is not less than 30 nm and not more than 45 nm.
(2) The film thickness of the TaPd-based film is 8 nm or more and 36 nm or less.
(3) The peak reflectance of EUV light on the surface of the absorption layer is 5% or more and 12% or less.
(4) The phase difference (φ) between the EUV reflected light on the surface of the reflective layer and the EUV reflected light on the surface of the absorbing layer is in the range of 180 ° ± 10 °.
(5) The gradient (Δφ / ΔL) of the change (Δφ) in the phase difference (φ) with respect to the change (ΔL) in the total film thickness (L) of the absorption layer is 15 deg / nm or less.   The Cr-based film is a CrN film containing chromium (Cr) and nitrogen (N), the Cr content is 40 to 97 at%, the N content is 3 to 60 at%, the Cr and The reflective mask blank for EUV lithography according to claim 1, wherein the total content of N is 95 to 100 at%.   The TaPd-based film is a TaPdN film containing tantalum (Ta), palladium (Pd) and nitrogen (N), the Ta content is 10 to 60 at%, and the Pd content is 20 to 70 at%. The reflective mask blank for EUV lithography according to claim 1, wherein the N content is 10 to 70 at%, and the total content of Ta, Pd, and N is 95 to 100 at%.   At least one of the Cr-based film and the TaPd-based film further contains hydrogen (H), silicon (Si), and boron (B) at a total content of 0.1 to 10 at%. Item 4. A reflective mask blank for EUV lithography according to any one of Items 1 to 3.   The upper layer has a two-layer structure of the CrN film and a surface protective layer formed on the CrN film, the surface protective layer contains Cr and O, and the Cr content is 15 to 70 at%. Yes, a CrO film having an O content of 30 to 85 at%, or containing Cr, O and N, a Cr content of 10 to 60 at%, and a total content of O and N of 40 to 90 at% The reflective mask blank for EUV lithography according to any one of claims 2 to 4, wherein the reflective mask blank is a CrON film having a composition ratio of O and N of O: N = 9: 1 to 6: 4.   The upper layer has a two-layer structure of the TaPdN film and a surface protective layer formed on the TaPdN film, the surface protective layer contains Ta, Pd and O, and the O content is 30 to 85 at. % TaPdO film or Ta, Pd, O and N, the total content of O and N is 40 to 90 at%, and the composition ratio of O and N is O: N = 9: 1 to 6: The reflective mask blank for EUV lithography according to claim 3, which is a TaPdON film of 4.   The EUV lithography according to claim 6, wherein the TaPdO film has a Ta content of 7 to 32 at%, a Pd content of 8 to 38 at%, and an O content of 30 to 85 at%. Reflective mask blank.   The TaPdON film has a Ta content of 5 to 27 at%, a Pd content of 5 to 33 at%, a total content of O and N of 40 to 90 at%, and a composition of O and N The reflective mask blank for EUV lithography according to claim 6, wherein the ratio is O: N = 9: 1 to 6: 4.   The reflective mask blank for EUV lithography according to any one of claims 5 to 8, wherein the film thickness of the surface protective layer is 0.5 nm or more and 5 nm or less.   The EUV lithography according to claim 5, wherein the surface protective layer further contains hydrogen (H), silicon (Si), and boron (B) at a total content of 0.1 to 10 at%. Reflective mask blank.   The reflective mask blank for EUV lithography according to any one of claims 1 to 10, wherein the crystalline state of the absorption layer is amorphous.   The reflective mask blank for EUV lithography according to any one of claims 1 to 11, wherein the surface roughness (rms) of the absorption layer surface is 0.5 nm or less. A protective layer is formed between the reflective layer and the absorbing layer to protect the reflective layer when forming a pattern on the absorbing layer.
The reflective mask blank for EUV lithography according to any one of claims 1 to 12, wherein the protective layer comprises Ru or a Ru compound as a constituent material.   The reflective mask blank for EUV lithography according to claim 13, wherein the upper layer is the TaPd-based film and the lower layer is the Cr-based film. The Cr-based film is a CrN film, and the CrN film includes at least one of helium (He), argon (Ar), neon (Ne), krypton (Kr), and xenon (Xe), and nitrogen (N ₂ ). The method for producing a reflective mask blank for EUV lithography according to claim 2, wherein the sputtering method is performed using a target containing chromium (Cr) in an inert gas atmosphere including : The TaPd-based film is a TaPdN film, and the TaPdN film includes at least one of helium (He), argon (Ar), neon (Ne), krypton (Kr), and xenon (Xe), and nitrogen (N ₂ And an inert gas atmosphere containing tantalum (Ta) and palladium (Pd) in an inert gas atmosphere. A method for manufacturing a reflective mask blank. The surface protective layer is a TaPdO film, and the TaPdO film includes at least one of helium (He), argon (Ar), neon (Ne), krypton (Kr), and xenon (Xe), and oxygen (O ₂ ). The EUV lithography according to claim 6, wherein the sputtering method is performed using a target containing tantalum (Ta) and palladium (Pd) in an inert gas atmosphere containing manufacturing method of use reflective mask blank. The surface protective layer is a TaPdON film, and the TaPdON film includes at least one of helium (He), argon (Ar), neon (Ne), krypton (Kr), and xenon (Xe), and oxygen (O ₂ ). And an inert gas atmosphere containing nitrogen (N ₂ ) and a sputtering method using a target containing tantalum (Ta) and palladium (Pd). The manufacturing method of the reflective mask blank for EUV lithography of 8. The surface protective layer is a CrO film, and the CrO film includes at least one of helium (He), argon (Ar), neon (Ne), krypton (Kr), and xenon (Xe), and oxygen (O ₂ ). The method for producing a reflective mask blank for EUV lithography according to claim 5, wherein a sputtering method is performed using a target containing chromium (Cr) in an inert gas atmosphere including : The surface protective layer is a CrON film, and the CrON film includes at least one of helium (He), argon (Ar), neon (Ne), krypton (Kr), and xenon (Xe), and oxygen (O ₂ ). The reflective mask for EUV lithography according to claim 5, which is formed by performing a sputtering method using a target containing chromium (Cr) in an inert gas atmosphere containing nitrogen and nitrogen (N ₂ ). Blank manufacturing method . Claim. 1 to 14 for EUV lithography reflective mask was subjected to patterning the absorber layer of the reflective mask blank for EUV lithography according to any one of.